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Solar panel calculator 1.1 user interface


The solar panel angle calculator is not only a
web calculator for calculating the ideal angle of solar panel
installation, for which it was originally intended. Now it is a small
but powerful web application that, based on the entered data,
calculates the amount of electricity you can get on your property if
You are thinking about investing in solar energy on your property. At
the same time, possession can be 1. Your house’s roof that faces
south completely or partially. 2. Unused land (a meadow, an ice
yard, or similar) for a mini solar power plant


Data to be entered for solar panel calclulation

In both of the preceding cases, three key pieces
of information must be entered:

  • Geographical latitude (you don’t need to know it; you need to choose
    from the offered options of larger cities nearby)
  • The pitch angle of your roof
  • South orientation (only for the first case) If the panel is mounted
    on the roof of the house facing completely or partially to the south.

It is necessary (for the northern hemisphere) that the roof of the
house faces south, south-east, or south-west. If the roof faces the
other way (north, northwest, or northeast), the investment is
unprofitable, and this is not taken into account. It will rarely
happen that the roof is facing exactly south, but rather deviates to
the west or east. It is necessary to measure this angle of deviation
from the axis that is directed toward the south.

The roof of the house dictates the slope of the fixed panel.

Those three main parameters are immutable, and they dictate the conditions
in this case. If they were to build a mini-solar power plant on unused land If you
have a plot or yard where there are no trees or similar obstacles  that create shade, it is possible to use the same space for a mini
solar power plant. In this case, you can adjust the tilt angle of the
panel and the orientation yourself. The only factor that you cannot
influence is the latitude of the location.

  • You can choose between three options for building a mini solar power
    South-facing panels have a fixed tilt angle.
  • with an adjustable monthly tilt angle facing south (single axis
  • •with an adjustable tilt angle of the panel and position that
    follows the sun during the day (two-axis tracker).

The simplest case is a fixed angle of the panels facing south. You can get the tilt angle as part of the SPAC web application calculation,
and you can also get the ideal angles of the monthly positions of the
solar panels for the case of a single axis tracker.


Program versions of Solar Panel Angle Calulator

Version 0.9 beta of the SPAC program, released
in October 2022, calculated the theoretical results of angles and
irradiation based on three main parameters.

1.0 beta (December 2022): the program has been improved, and options
have been added to calculate the expected amount of electricity based
on the roof of the house or the desired mini solar power plant. The
classical Liu-Joradan method system for the diffuse component and the
turbidity coefficient were used for the calculation.

1.1 beta, January 2022: the program was improved with an algorithm
for the stochastic calculation of the turbidity coefficient based on
statistical results, developed by site author mechanical engineer
Miroslav Mitic.

All versions are beta releases because they are still in the testing
phase. The algorithm is stable, but there are possibilities of small
errors when entering statistics.


Solar Panel calculator user interface

The user interface consists of six parts:

  1. Choosing the nearest location or manually entering latitude; in the other case, the result is only  theoretical values. This entry is required. Below it is a list box from which we choose the appearance of the environment, which is important only for the calculation of the reflected component.

2. Panel options: in the non-commercial version, only fixed panels are  counted. Do not change anything there.

3. Entry of the slope of the roof of the house or panel and orientation  a deviation from the south side. If the deviation is in  the south-southeast direction, values from -1 to -90 are entered; if the deviation is in the southwest direction, values from 1 to 90 are entered. It is measured from the axis pointing south!

These two values are required. 

4. Panel selection and placement options This is the program’s most interesting and useful option. It was introduced in version beta 1.
First, a splash panel is selected from the drop-down list. In the database, there are some solar panels of different powers or dimensions. You can decide how you want to judge whether it will fit dimensionally or in the intended investment. And in this case, there are two options. Check the following box:

4.1 The option of mounting the panels on a fixed roof It is understood that the roof faces south completely or partially and that there are
no obstacles on it (skylights, antennas, chimneys, or similar sources of shadow). Then divide the length by the width of the roof.

4.2 The option of mounting a grid of salad panels You can design your own MXN panel grid and install as many as you want on the roof or flat surface. In the second case, it is preferable when you already have the possibility to orient the panels towards the south.

5. Calculation and setting option You can choose the type of calculation in this section. My system consists of the stochastic modified Liu-Joradn method (the default), and you can also choose a classic calculation system. After entering all the data, the results are obtained by selecting the “Calculate” button.


City select


Roof tilt and oriention to the South



The result consists of two parts: theoretical and real, i.e., the estimation of the gain of electrical energy. More details in the RESULTS page



The user interface is very simple and even fun. The program is quite powerful, and you can try various PV module placement options and get quite precise results. The disadvantage of the program is that only larger places for which there are statistical analyses of weather conditions are covered, but this will be corrected in future versions of the program..


Miroslav Mitić

Mechanical engineer and programmer for 25 years. Solar energy expert

This Post Has 2 Comments

  1. admin

    Thank you for the information on the Solar panel calculator user interface. That was perfect. I am interested in the solar panel. All the details are important. I will share this with my friends now I understand more that it takes a lot of work. All the details are a must-correct. Good to know more, And I have the correct information from you. Thanks again,

    1. mmitic

      Thank you for your kind words. I try to simplify and demystify the terms related to the implementation of solar energy, which I believe is an inevitable source of energy for generations after us. That is my mission, as well as some form of redemption for them. Thanks again

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